Polyamide resin, and polymer film, resin laminate using the same

ABSTRACT

The present invention relates to a polyamide resin in which an average particle size of individual crystals measured by a small-angle X-ray scattering apparatus is 8.0 nm or less, and a polymer film and resin laminate using the same.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a 35 U.S.C. 371 National Phase Entry Applicationfrom PCT/KR2019/014716, filed on Nov. 1, 2019, designating the UnitedStates, which claims the benefit of priority from Korean PatentApplication No. 10-2018-0134755 filed on Nov. 5, 2018; Korean PatentApplication No. 10-2018-0153911 filed on Dec. 3, 2018; Korean PatentApplication No. 10-2019-0014022 filed on Feb. 1, 2019; Korean PatentApplication No. 10-2019-0034611 filed on Mar. 26, 2019; Korean PatentApplication No. 10-2019-0125890 filed on Oct. 11, 2019; Korean PatentApplication No. 10-2019-0137544 filed on Oct. 31, 2019; and KoreanPatent Application No. 10-2019-0137545 filed on Oct. 31, 2019 in theKorean Intellectual Property Office, the disclosures of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a polyamide resin that can secure atleast an adequate level of mechanical properties while improvingtransparency by suppressing excessive growth of the length ofcrystalline polymer chains, and a polymer film and resin laminate usingthe same.

BACKGROUND OF THE INVENTION

Aromatic polyimide resins are polymers mostly having an amorphousstructure, and exhibits excellent heat resistance, chemical resistance,electrical properties, and dimensional stability due to their rigidchain structure. Thus, these polyimide resins are widely used asmaterials for electric/electronics.

However, the polyimide resins have many limitations in their use becausethey may appear dark brown in color due to charge transfer complex (CTC)formation of Pi-electrons present in the imide chain, and it isdifficult to secure transparency. In the case of the polyimide filmincluding the same, it has a drawback in that the surface is easilyscratched and scratch resistance is very weak.

In order to solve the above limitation of the polyimide resin, studieson polyamide resins into which an amide group is introduced has beenactively conducted. The amide structure induces intermolecular orintramolecular hydrogen bonds, resulting in improvement of scratchresistance by interactions such as hydrogen bonds.

However, due to the difference in solubility, reactivity (sterichindrance), and reaction rate of terephthaloyl chloride or isophthaloylchloride used for the synthesis of the polyamide resin, amide repeatingunits derived from terephthaloyl chloride and amide repeating unitsderived from isophthaloyl chloride do not form a block, and are hardlypolymerized ideally or alternatively.

Therefore, there is a limit that as the block of amide repeating unitsderived from the para acyl chloride monomer is formed and thecrystallinity of the polyamide resin increases, the transparency becomespoor due to haze.

In addition, as the monomers used for the synthesis of the polyamideresin perform the polymerization reaction in a state dissolved in asolvent, the molecular weight of the finally synthesized polyamide resinis difficult to be ensured to a sufficient level due to deterioration bymoisture or hybridization with a solvent.

Accordingly, there is a continuing need to develop a polyamide resincapable of realizing transparency and mechanical propertiessimultaneously.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a polyamide resin that can secure atleast an adequate level of mechanical properties while improvingtransparency by suppressing excessive growth of the length ofcrystalline polymer chains.

The present invention also provides a polymer film and resin laminateusing the aforementioned polyamide resin.

One aspect of the present invention provides a polyamide resin in whichan average particle size of individual crystals measured by asmall-angle X-ray scattering apparatus is 8.0 nm or less.

Another aspect of the present invention provides a polymer filmincluding the aforementioned polyamide resin.

Yet another aspect of the present invention provides a resin laminateincluding a substrate including a polyamide resin in which an averageparticle size of individual crystals measured by a small-angle X-rayscattering apparatus is 8.0 nm or less; and a hard coating layer formedon at least one side of the substrate.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a polyamide resin and a polymer film and resin laminateusing the same according to specific embodiments of the presentinvention will be described in more detail.

Unless explicitly stated otherwise, the terminology used herein may bedefined as follows.

Throughout the specification, when one part “includes” one constituentelement, unless otherwise specifically described, this does not meanthat another constituent element is excluded, but means that anotherconstituent element may be further included.

In the present specification, examples of the substituents are describedbelow, but are not limited thereto.

As used herein, the term “substituted” means that other functionalgroups instead of a hydrogen atom in the compound are bonded, and aposition to be substituted is not limited as long as the position is aposition at which the hydrogen atom is substituted, that is, a positionat which the substituent can be substituted, and when two or more aresubstituted, the two or more substituents may be the same as ordifferent from each other.

As used herein, the term “substituted or unsubstituted” means beingunsubstituted or substituted with one or more substituents selected fromthe group consisting of deuterium; a halogen group; a cyano group; anitro group; a hydroxyl group; a carbonyl group; an ester group; animide group; an amide group; a primary amino group; a carboxy group; asulfonic acid group; a sulfonamide group; a phosphine oxide group; analkoxy group; an aryloxy group; an alkylthioxy group; an arylthioxygroup; an alkylsulfoxy group; an arylsulfoxy group; a silyl group; aboron group; an alkyl group; a haloalkyl group; a cycloalkyl group; analkenyl group; an aryl group; an aralkyl group; an aralkenyl group; analkylaryl group; an alkoxysilylalkyl group; an arylphosphine group; or aheterocyclic group containing at least one of N. O, and S atoms, orbeing unsubstituted or substituted with a substituent to which two ormore substituents are linked among the substituents exemplified above.For example, “the substituent to which two or more substituents arelinked” may be a biphenyl group. That is, the biphenyl group may also bean aryl group, and may be interpreted as a substituent to which twophenyl groups are linked. Preferably, a haloalkyl group can be used asthe substituent, and examples of the haloalkyl group includetrifluoromethyl group.

As used herein, the notation

, or

mean a bond linked to another substituent group, and a direct bond meansthe case where no other atoms exist in the parts represented as L.

In the present specification, the alkyl group is a monovalent functionalgroup derived from an alkane, and may be a straight-chain or abranched-chain. The number of carbon atoms of the straight chain alkylgroup is not particularly limited, but is preferably 1 to 20. Also, thenumber of carbon atoms of the branched chain alkyl group is 3 to 20.Specific examples of the alkyl group include methyl, ethyl, propyl,n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl,1-methyl-butyl, 1-ethyl-butyl, pentyl, n-pentyl, isopentyl, neopentyl,tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl,4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl, n-heptyl,1-methylhexyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl,2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethyl-propyl,1,1-dimethyl-propyl, isohexyl, 2-methylpentyl, 4-methylhexyl,5-methylhexyl, 2,6-dimethylheptane-4-yl and the like, but are notlimited thereto.

In the present specification, the aryl group is a monovalent functionalgroup derived from an arene, and is not particularly limited, butpreferably has 6 to 20 carbon atoms, and may be a monocyclic aryl groupor a polycyclic aryl group. The monocyclic aryl group may include, butnot limited to, a phenyl group, a biphenyl group, a terphenyl group, orthe like. The polycyclic aryl group may include, but not limited to, anaphthyl group, an anthracenyl group, a phenanthryl group, a pyrenylgroup, a perylenyl group, a chrysenyl group, a fluorenyl group or thelike. The aryl group may be substituted or unsubstituted.

In the present specification, the arylene group is a bivalent functionalgroup derived from an arene, and the description of the aryl group asdefined above may be applied, except that it is a divalent functionalgroup. For example, it may be a phenylene group, a biphenylene group, aterphenylene group, a divalent naphthalene group, a divalent fluorenylgroup, a divalent pyrenyl group, a divalent phenanthrenyl group, adivalent perylene group, a divalent tetracenyl group, an divalentanthracenyl group and the like. The arylene group may be substituted orunsubstituted.

In the present specification, a heteroaryl group includes one or moreatoms other than carbon, that is, one or more heteroatoms, andspecifically, the heteroatom may include one or more atoms selected fromthe group consisting of O, N, Se, and S, and the like. The number ofcarbon atoms thereof is not particularly limited, but is preferably 4 to20, and the heteroaryl group may be monocyclic or polycyclic. Examplesof a heterocyclic group include a thiophene group, a furanyl group, apyrrole group, an imidazolyl group, a thiazolyl group, an oxazolylgroup, an oxadiazolyl group, a pyridyl group, a bipyridyl group, apyrimidyl group, a triazinyl group, a triazolyl group, an acridyl group,a pyridazinyl group, a pyrazinyl group, a quinolinyl group, aquinazolinyl group, a quinoxalinyl group, a phthalazinyl group, apyridopyrimidinyl group, a pyridopyrazinyl group, a pyrazinopyrazinylgroup, an isoquinolinyl group, an indolyl group, a carbazolyl group, abenzoxazolyl group, a benzimidazolyl group, a benzothiazolyl group, abenzocarbazolyl group, a benzothiophene group, a dibenzothiophene group,a benzofuranyl group, a phenanthrolinyl group (phenanthroline), athiazolyl group, an isoxazolyl group, an oxadiazolyl group, athiadiazolyl group, a benzothiazolyl group, a phenothiazinyl group, anaziridinyl group, an azaindolyl group, an isoindolyl group, an indazolylgroup, a purine group (purine), a pteridinyl group (pteridine), abeta-carboline group, a naphthyridinyl group (naphthyridine), ater-pyridyl group, a phenazinyl group, an imidazopyridyl group, apyropyridyl group, an azepine group, a pyrazolyl group, a dibenzofuranylgroup, and the like, but are not limited thereto. The heteroaryl groupmay be substituted or unsubstituted.

In the present specification, the hetero arylene group has 2 to 20, or 2to 10, or 6 to 20 carbon atoms. For the arylene group containing 0, N orS as a hetero atom, the description of the heteroaryl group as definedabove can be applied except that it is a divalent functional group. Thehetero arylene group may be substituted or unsubstituted.

In this specification, examples of halogen include fluorine, chlorine,bromine or iodine.

I. Polyamide Resin

According to one embodiment of the present invention, there can beprovided a polyamide resin in which an average particle size ofindividual crystals measured by a small-angle X-ray scattering apparatusis 8.0 nm or less.

The present inventors have found through experiments that as thepolyamide resin in which an average particle size of individual crystalsis 8.0 nm or less as described above not only has excellent mechanicalproperties possessed by a crystalline polymer but also the growth ofindividual crystals forming the crystal structure slows down to have arelatively small size, whereby it has a remarkably low level of hazevalue, yellowness, etc., and additionally can have high flexibility andbending durability, thereby completing the present invention.

Unlike this, when the average particle size of individual crystalsmeasured for the polyamide resin by a small-angle X-ray scatteringapparatus increases excessively by 8.0 nm or more, the ratio occupied bythe portion having crystallinity in the polyamide resin or the sizethereof is excessively grown, whereby the crystal characteristic isstrongly implemented, the flexibility or bending durability of thepolymer itself is lowered, the haze value is rapidly increased and sothe transparency can be lowered.

Specifically, the polyamide resin can satisfy an average particle sizeof individual crystals of 8.0 nm or less as measured by a small-angleX-ray scattering apparatus. The polyamide resin may include a pluralityof individual crystals. The average particle size of the individualcrystals contained in the polyamide resin can be determined through themethod for calculating the number average particle size which includesconfirming the particle sizes of all the crystals contained in thepolyamide resin and then dividing the sum of these particle sizes by thenumber of individual crystals.

The average particle size of the individual crystals can be measuredthrough an analytical equipment by fitting a scattering pattern obtainedby irradiating X-rays with energies of 10 KeV to 20 KeV, or 10 KeV to 14KeV, or 16 KeV to 20 KeV in a small-angle X-ray scattering apparatus toa solid sphere model.

As for the X-rays to be irradiated, for example, a method of irradiatingX-rays with energies of 10 KeV to 14 KeV and X-rays together withenergies of 16 KeV to 20 KeV can be used.

The scattering pattern, which is the data obtained from the small-angleX-ray scattering apparatus, may be a result measured by irradiatingX-rays with energies of 10 KeV to 20 KeV using the small-angle X-rayscattering apparatus at a temperature of 20° C. to 30° C. As a detectorin the small-angle X-ray scattering apparatus, an imaging plate, aposition-sensitive detector (PSPC), and the like can be used.

Subsequently, an average particle size analysis of the individualcrystals may be performed through an analytical equipment that isseparately installed inside or outside the small-angle X-ray scatteringapparatus. An example of the small-angle X-ray scattering apparatus maybe a PLS 9A beamline, and an example of the analytical equipment may bea NIST SANS package which is a computer program.

Specifically, the average particle size of the individual crystals canbe determined through the calculation of computer program (NIST SANSpackage) for the diameter distribution curve of crystals which isobtained by fitting the shape of individual crystals contained in thesample to a solid sphere model, plotting the obtained wavenumber q(unit: Å⁻¹) and scattering intensity I (unit: a.u.), and convoluting theplot with a Schulz-Zimm distribution.

The crystals can be a group of individual crystals having a particlesize of 0.1 nm to 15 nm, and the individual crystals contained in suchgroup can have an average particle size of 8 nm or less. Morespecifically, 95%, or 99% of the individual crystals contained in thegroup may have a particle size of 8 nm or less. That is, as the majorityof the individual crystals has a particle size of 0.8 nm or less, or 7nm or less, or 0.1 nm to 8.0 nm, or 0.1 nm to 7 nm, or 1 nm to 8 nm, or1 nm to 7 nm, or 3 nm to 8 nm, or 3 nm to 7 nm, or 5 nm to 6.8 nm, theaverage particle size of the individual crystals may also satisfy theabove-mentioned range.

More specifically, the average particle size of the individual crystalsmeasured by the small-angle X-ray scattering apparatus may be 8.0 nm orless, or 7 nm or less, or 0.1 nm to 8.0 nm, or 0.1 nm to 7 nm, or 1 nmto 8 nm, Or 1 nm to 7 nm, or 3 nm to 8 nm, or 3 nm to 7 nm, or 5 nm to6.8 nm.

Specifically, when the polyamide resin sample is irradiated with X-raysusing the small-angle X-ray scattering apparatus, the small-angle X-rayscattering pattern is secured through a detector. When analyzing thisthrough an analytical equipment, it is possible to determine the averageradius (Rc) of the individual crystals contained in the polyamide resinsample. Through this, finally, the average particle size of theindividual crystals can be determined by calculating twice the averageradius (Rc) of the individual crystals described above.

More specifically, with reference to the crystal structure of thepolyamide resin of one embodiment described in FIG. 1 below, thepolyamide resin is composed of amorphous polymer chains 3 presentbetween individual crystals, together with a plurality of individualcrystals 1, and a particle size 2 can be defined for the individualcrystals.

On the other hand, the individual crystals 1 may be formed by gatheringpolyamide resin chains in a bundle, as shown in FIG. 4. In particular,the length of the individual crystals can be grown through the overlapbetween the crystalline polymer blocks contained in the polyamide resin.It is difficult to specifically specify the shape of the overlappedindividual crystals, but it can be seen that it has roughly a spherulitestructure by three-dimensional growth, a lamella structure bytwo-dimensional growth, or an intermediate structure betweenthree-dimensional and two-dimensional.

Preferably, the polyamide resin may have a dimensionality of theindividual crystals measured by a small-angle X-ray scattering apparatusof 3.0 or more, or 3.0 to 4.0. The dimensionality of the individualcrystals of the polyamide resin can be measured through an analyticalinstrument by fitting a spherical scattering pattern obtained byirradiating X-rays with energies of 10 KeV to 20 KeV, or 10 KeV to 14KeV, or 16 KeV to 20 KeV in a small-angle X-ray scattering apparatus toa solid sphere model. The small-angle X-ray scattering apparatus and thecontents of the analysis thereon include the contents described above inthe average particle size of the individual crystals.

Meanwhile, the polyamide resin may further include amorphous polymerchains present between the individual crystals having an averageparticle size of 8.0 nm or less. More specifically, with reference tothe crystal structure of the polyamide resin of one embodiment describedin FIG. 1 below, the polyamide resin may be composed of amorphouspolymer chains 3 present between individual crystals together with aplurality of individual crystals 1.

Due to the amorphous polymer chains, the growth of the average particlesize of the individual crystals is suppressed, and the polyamide resinmay satisfy an average particle size of individual crystals measured bya small-angle X-ray scattering apparatus of 8.0 nm or less.

In this case, the distance between the individual crystals having anaverage particle size of 8.0 nm or less may be 0.1 nm to 100 nm, or 1 nmto 100 nm, or 30 nm to 100 nm. The distance between individual crystalshaving an average particle size of 8.0 nm or less can also be measuredby a small-angle X-ray scattering apparatus.

In the polyamide resin, examples of specific components of theindividual crystals whose average particle size measured by asmall-angle X-ray scattering apparatus is 8.0 nm or less are notparticularly limited, and various aromatic amide repeating units used inthe preparation of crystalline polyamide resins can be applied withoutlimitation.

As an example of the component of the individual crystals whose averageparticle size measured by the small-angle X-ray scattering apparatus is8.0 nm or less, a first aromatic polyamide repeating unit derived from acombination of a 1,4-aromatic diacyl compound and an aromatic diaminecompound may be included. The polymer chains composed of the firstaromatic amide repeating units may be gathered in a bundle to formindividual crystals having an average particle size of 8.0 nm or less.

Specific examples of the 1,4-aromatic diacyl compound includeterephthaloyl chloride or terephthalic acid. In addition, examples ofthe aromatic diamine monomer may include at least one selected from thegroup consisting of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine,2,2′-dimethyl-4,4′-diaminobenzidine, 4,4′-diaminodiphenyl sulfone,4,4′-(9-fluorenylidene)dianiline, bis(4-(4-aminophenoxy)phenyl)sulfone,2,2′,5,5′-tetrachlorobenzidine, 2,7-diaminofluorene,4,4-diaminooctafluorobiphenyl, m-phenylenediamine, p-phenylenediamine,4,4′-oxydianiline, 2,2′-dimethyl-4,4′-diaminobiphenyl,2,2-bis[4-(4-aminophenoxy)phenyl]propane,1,3-bis(4-aminophenoxy)benzene, m-xylylenediamine, p-xylylenediamine and4,4′-diaminobenzanilide.

Preferably the 1,4-aromatic diacyl compound may include terephthaloylchloride, or terephthalic acid, and the aromatic diamine compound mayinclude 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine.

More specifically, the individual crystals having an average particlesize of 8.0 nm or less may include a first polyamide segment including arepeating unit represented by the following Chemical Formula 1, or ablock comprised thereof.

in Chemical Formula 1, Ar₁ is a substituted or unsubstituted arylenegroup having 6 to 20 carbon atoms, or a substituted or unsubstitutedheteroarylene group having 2 to 20 carbon atoms.

In Chemical Formula 1, Ar₁ is an arylene group having 6 to 20 carbonatoms that is substituted with one or more substituents selected fromthe group consisting of an alkyl group, a haloalkyl group, and an aminogroup, and more preferably, it may be a2,2′-bis(trifluoromethyl)-4,4′-biphenylene group.

More specifically, in Chemical Formula 1, Ar₁ may be a divalent organicfunctional group derived from an aromatic diamine monomer, and specificexamples of the aromatic diamine monomer may include at least oneselected from the group consisting of2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine,2,2′-dimethyl-4,4′-diaminobenzidine, 4,4′-diaminodiphenyl sulfone,4,4′-(9-fluorenylidene)dianiline, bis(4-(4-aminophenoxy)phenyl)sulfone,2,2′,5,5′-tetrachlorobenzidine, 2,7-diaminofluorene,4,4-diaminooctafluorobiphenyl, m-phenylenediamine, p-phenylenediamine,4,4′-oxydianiline, 2,2′-dimethyl-4,4′-diaminobiphenyl,2,2-bis[4-(4-aminophenoxy)phenyl]propane,1,3-bis(4-aminophenoxy)benzene, and 4,4′-diaminobenzanilide. Morepreferably, the aromatic diamine monomer may be2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine(TFDB) or2,2′-dimethyl-4,4′-diaminobenzidine.

The first polyamide segment may include a repeating unit represented byChemical Formula 1, or a block composed of a repeating unit representedby Chemical Formula 1.

Specific examples of the repeating unit represented by Chemical Formula1 include a repeating unit represented by the following Chemical Formula1-1.

The repeating unit represented by Chemical Formula 1 is an amiderepeating unit derived from a combination of a 1,4-aromatic diacylcompound and an aromatic diamine compound, specifically, an amiderepeating unit formed by an amidation reaction of terephthaloyl chlorideor terephthalic acid with an aromatic diamine monomer. Due to the linearmolecular structure, the chain packing and alignment can be keptconstant in the polymer, and the surface hardness and mechanicalproperties of the polyamide film can be improved.

Specific examples of the 1,4-aromatic diacyl compound includeterephthaloyl chloride or terephthalic acid. In addition, examples ofthe aromatic diamine monomer may include at least one selected from thegroup consisting of 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine),2,2′-dimethyl-4,4′-diaminobenzidine, 4,4′-diaminodiphenyl sulfone,4,4′-(9-fluorenylidene)dianiline, bis(4-(4-aminophenoxy)phenyl)sulfone),2,2′,5,5′-tetrachlorobenzidine, 2,7-diaminofluorene,4,4-diaminooctafluorobiphenyl, m-phenylenediamine, p-phenylenediamine,4,4′-oxydianiline, 2,2′-dimethyl-4,4′-diaminobiphenyl,2,2-bis[4-(4-aminophenoxy)phenyl]propane,1,3-bis(4-aminophenoxy)benzene, m-xylylenediamine, p-xylylenediamine and4,4′-diaminobenzanilide.

Preferably the 1,4-aromatic diacyl compound may include terephthaloylchloride, or terephthalic acid, and the aromatic diamine compound mayinclude 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine.

The first polyamide segment may have a number average molecular weightof 100 g/mol to 5000 g/mol, or 100 g/mol to 3000 g/mol, or 100 g/mol to2500 g/mol, or 100 g/mol to 2450 g/mol. When the number averagemolecular weight of the first polyamide segment is increased by morethan 5000 g/mol, the chains of the first polyamide segment becomeexcessively long and so the crystallinity of the polyamide resin can beincreased. As a result, it may have a high haze value and so it may bedifficult to secure transparency. Examples of the measuring method ofthe number average molecular weight of the first polyamide segment isnot limited, but for example, it can be confirmed through a small-angleX-ray scattering (SAXS) analysis.

The first polyamide segment may be represented by the following ChemicalFormula 5.

in Chemical Formula 5, Ar₁ is a substituted or unsubstituted arylenegroup having 6 to 20 carbon atoms, or a substituted or unsubstitutedheteroarylene group having 2 to 20 carbon atoms, and a is an integer of1 to 5. In Chemical Formula 5, when a is 1, the Formula 5 may be arepeating unit represented by Chemical Formula 1. In Chemical Formula 5,when a is 2 to 5, the Formula 5 may be a block composed of repeatingunits represented by Chemical Formula 1. In Chemical Formula 5, thedetails concerning Ar₁ includes those described above in ChemicalFormula 1.

Based on the total repeating units contained in the polyamide resin, theratio of the repeating units represented by Chemical Formula 1 may be 40mol % to 95 mol %, 50 mol % to 95 mol %, or 60 mol % to 95 mol %, or 70mol % to 95 mol %, or 50 mol % to 90 mol %, or 50 mol % to 85 mol %, or60 mol % to 85 mol %, or 70 mol % to 85 mol %, or 80 mol % to 85 mol %,or 82 mol % to 85 mol %.

In this manner, the polyamide resin in which the repeating unitrepresented by Chemical Formula 1 is contained in the above-describedcontent can ensure a sufficient level of molecular weight, therebyensuring excellent mechanical properties.

Further, in the polyamide resin, examples of specific components of theamorphous polymer chains present between the individual crystals havingan average particle size of 8.0 nm or less are not particularly limited,and various aromatic amide repeating units used in the preparation ofamorphous polyamide resins can be applied without limitation.

Examples of an amorphous polymer chain component present betweenindividual crystals whose average particle size measured by thesmall-angle X-ray scattering apparatus is 8.0 nm or less may include asecond aromatic amide repeating units derived from a combination of a1,2-aromatic diacyl compound and an aromatic diamine compound, or athird aromatic amide repeat unit derived from a combination of a1,3-aromatic diacyl compound and an aromatic diamine compound, ormixtures thereof. The polymer chains composed of the second aromaticamide repeating unit or the third aromatic amide repeating unit asdescribed above may realize amorphous characteristics.

Specific examples of the 1,2-aromatic diacyl compound include phthaloylchloride or phthalic acid. In addition, specific examples of the1,3-aromatic diacyl compound include isophthaloyl chloride orisophthalic acid. Examples of the aromatic diamine monomer include atleast one selected from the group consisting of2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine,2,2′-dimethyl-4,4′-diaminobenzidine, 4,4′-diaminodiphenyl sulfone,4,4′-(9-fluorenylidene)dianiline, bis(4-(4-aminophenoxy)phenyl)sulfone,2,2′,5,5′-tetrachlorobenzidine, 2,7-diaminofluorene,4,4-diaminooctafluorobiphenyl, m-phenylenediamine, p-phenylenediamine,4,4′-oxydianiline, 2,2′-dimethyl-4,4′-diaminobiphenyl,2,2-bis[4-(4-aminophenoxy)phenyl]propane,1,3-bis(4-aminophenoxy)benzene, m-xylylenediamine, p-xylylenediamine and4,4′-diaminobenzanilide.

Preferably the 1,2-aromatic diacyl compound may include phthaloylchloride, or phthalic acid, the 1,3-aromatic diacyl compound may includeisophthaloyl chloride or isophthalic acid, and the aromatic diaminecompound may include 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine.

More specifically, the amorphous polymer chains present between theindividual crystals having an average particle size of 8.0 nm or lessincluding the first polyamide segment including a repeating unitrepresented by Chemical Formula 1 or a block composed thereof mayinclude a second polyamide segment including a repeating unitrepresented by the following Chemical formula 2, or a block composedthereof.

in Chemical Formula 2, Ar₂ is a substituted or unsubstituted arylenegroup having 6 to 20 carbon atoms, or a substituted or unsubstitutedheteroarylene group having 2 to 20 carbon atoms.

In Chemical Formula 2, Ar₂ is an arylene group having 6 to 20 carbonatoms that is substituted with one or more substituents selected fromthe group consisting of an alkyl group, a haloalkyl group, and an aminogroup. More preferably, it may be a2,2′-bis(trifluoromethyl)-4,4′-biphenylene group.

More specifically, in Chemical Formula 2, Ar₂ may be a divalent organicfunctional group derived from an aromatic diamine monomer. Specificexamples of the aromatic diamine monomer include at least one selectedfrom the group consisting of2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine,2,2′-dimethyl-4,4′-diaminobenzidine, 4,4′-diaminodiphenyl sulfone,4,4′-(9-fluorenylidene)dianiline, bis(4-(4-aminophenoxy)phenyl)sulfone,2,2′,5,5′-tetrachlorobenzidine, 2,7-diaminofluorene,4,4-diaminooctafluorobiphenyl, m-phenylenediamine, p-phenylenediamine,4,4′-oxydianiline, 2,2′-dimethyl-4,4′-diaminobiphenyl,2,2-bis[4-(4-aminophenoxy)phenyl]propane,1,3-bis(4-aminophenoxy)benzene, and 4,4′-diaminobenzanilide. Morepreferably, the aromatic diamine monomer may be2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB) or2,2′-dimethyl-4,4′-diaminobenzidine.

The second polyamide segment may include a repeating unit represented byChemical Formula 2, or a block composed of the repeating unitrepresented by Chemical Formula 2.

More specifically, the repeating unit represented by Chemical Formula 2may include one type of repeating unit selected from a repeating unitrepresented by the following Chemical Formula 2-1; or a repeating unitrepresented by Chemical Formula 2-2.

in Chemical Formulas 2-1 to 2-2, Ar₂ is a substituted or unsubstitutedarylene group having 6 to 20 carbon atoms, or a substituted orunsubstituted heteroarylene group having 2 to 20 carbon atoms. Thedetails concerning Ar₂ includes those described above in ChemicalFormula 2.

The repeating unit represented by Chemical Formula 2-1 is a repeatingunit formed by an amidation reaction of isophthaloyl chloride orisophthalic acid with an aromatic diamine monomer, and the repeatingunit represented by Chemical Formula 2-2 is a repeating unit formed byan amidation reaction of phthaloyl chloride or phthalic acid with anaromatic diamine monomer.

Specific examples of the repeating unit represented by Chemical Formula2-1 include a repeating unit represented by the following ChemicalFormula 2-4.

Specific examples of the repeating unit represented by Chemical Formula2-2 include a repeating unit represented by the following ChemicalFormula 2-5.

On the other hand, the second polyamide segment may be represented bythe 5 following Chemical Formula 6.

In Chemical Formula 6, Ar₂ is a substituted or unsubstituted arylenegroup having 6 to 20 carbon atoms, or a substituted or unsubstitutedheteroarylene group having 2 to 20 carbon atoms, and b is an integer of1 to 3 or 1 to 2. In Chemical Formula 6, when b is 1, the Formula 6 maybe a repeating unit represented by Chemical Formula 2. In ChemicalFormula 6, when b is 2 to 3, the Formula 6 may be a block composed ofrepeating units represented by Chemical Formula 2.

The repeating unit represented by Chemical Formula 2 is a repeating unitformed by an amidation reaction of isophthaloyl chloride, isophthalicacid or phthaloyl chloride, phthalic acid and an aromatic diaminemonomer. Due to the curved molecular structure, it has the property ofinterfering with chain packing and alignment within the polymer, and itis possible to increase the amorphous region in the polyamide resin andthus improve the optical properties and the folding endurance of thepolyamide film. In addition, as this is included in the polyamide resintogether with the repeating unit represented by Chemical Formula 1, itis possible to increase the molecular weight of the polyamide resin.

Based on the total repeating units contained in the polyamide resin, theratio of the repeating unit represented by Chemical Formula 2 may be 5mol % to 60 mol %, or 5 mol % to 50 mol %, or 5 mol % to 40 mol %, or 5mol % to 30 mol %, or 10 mol % to 50 mol %, or 15 mol % to 50 mol %, or15 mol % to 40 mol %, or 15 mol % to 30 mol %, or 15 mol % to 20 mol %,or 15 mol % to 18 mol %.

As described above, the polyamide resin in which the repeating unitrepresented by Chemical Formula 2 is contained in the above-describedcontent can suppress the length growth of the chains consisting of onlythe specific repeating unit represented by Chemical Formula 1 and thuslower the crystallinity of the resin. As a result, it is possible tohave a low haze value and thus secure excellent transparency.

More specifically, based on the total repeating units contained in thepolyamide resin, the content of the repeating unit represented byChemical Formula 1 may be 60 mol % to 95 mol %, or 70 mol % to 95 mol %,or 50 mol % to 90 mol %, or 50 mol % to 85 mol %, or 60 mol % to 85 mol%, or 70 mol % to 85 mol %, or 80 mol % to 85 mol %, or 82 mol % to 85mol %, and the content of the repeating unit represented by ChemicalFormula 2 may be 5 mol % to 40 mol %, or 5 mol % to 30 mol %, or 10 mol% to 50 mol %, or 15 mol % to 50 mol %, or 15 mol % to 40 mol %, or 15mol % to 30 mol %, or 15 mol % to 20 mol %, or 15 mol % to 18 mol %.

That is, the polyamide resin can increase the molar content of therepeating unit represented by Chemical Formula 1 and thus maximize theeffect of improving the surface hardness and mechanical properties ofthe polyamide film according to the chain packing and alignment withinthe polymer due to the linear molecular structure of the repeating unitrepresented by Chemical Formula 1. In addition, although the repeatingunit represented by Chemical Formula 2 has a relatively low molarcontent, it may suppress the length growth of the chains consisting ofonly the specific repeating unit represented by Chemical Formula 1,thereby lowering the crystallinity of the resin. As a result, it ispossible to have a low haze value and thus secure excellenttransparency.

On the other hand, the first polyamide segment and the second polyamidesegment may form a main chain including an alternating-repeating unitrepresented by the following Chemical Formula 3. That is, the firstpolyamide segment contained in the individual crystals whose averageparticle size measured by the small-angle X-ray scattering apparatus is8.0 nm or less may form an alternating-repeating unit represented by thefollowing Chemical Formula 3 with the second polyamide segment containedin the amorphous polymer chain existing between the individual crystals.

As a result, the polyamide resin of one embodiment has a structure inwhich a plurality of individual crystals and amorphous polymer chainsare repeated, as in the crystal structure shown in FIG. 1, and it ispossible to suppress the continuous size growth of only individualcrystals. Thereby, the individual crystals allow an average particlesize measured by a small-angle X-ray scattering apparatus to reduce to8.0 nm or less.

in Chemical Formula 3, A is the first polyamide segment, and B is thesecond polyamide segment.

Specifically, in the main chain of the polyamide resin, a firstpolyamide segment derived from terephthaloyl chloride or terephthalicacid and a second polyamide segment derived from isophthaloyl chloride,isophthalic acid or phthaloyl chloride, phthalic acid may alternatelyform a polymer chain as shown in Chemical Formula 3. That is, the secondpolyamide segment is positioned between the first polyamide segments,and may serve to suppress the growth of the length of the firstpolyamide segment.

The second polyamide segment is included in an amorphous polymer chainpresent between individual crystals having an average particle size of8.0 nm or less, and the first polyamide segment is included inindividual crystals having an average particle size of 8.0 nm or less.Therefore, in the polyamide resin, the amorphous polymer chain may bepositioned between individual crystals having an average particle sizeof 8.0 nm or less, and may serve to suppress the growth of the size ofthe individual crystals. This can also be confirmed through the crystalstructure shown in FIG. 1.

When the size growth of the individual crystals is suppressed in thismanner, it is possible to remarkably lower the haze value of thepolyamide resin while reducing crystal properties of the individualcrystals, thereby achieving excellent transparency.

On the other hand, “in the main chain of the polyamide resin, a firstpolyamide segment derived from terephthaloyl chloride or terephthalicacid and a second polyamide segment derived from isophthaloyl chloride,isophthalic acid or phthaloyl chloride, phthalic acid may alternatelyform a polymer chain as shown in Chemical Formula 3” is considered to bedue to the formation of a melt-kneaded complex in the preparation methodof the polyamide resin of the present invention described hereinafter.

When explanation is made by enumerating concrete examples, thealternating-repeating unit represented by Chemical Formula 3 may be arepeating unit represented by the following Chemical Formula 4.

in Chemical Formula 4, Ar₁ and Ar₂ are each independently a substitutedor unsubstituted arylene group having 6 to 20 carbon atoms, or asubstituted or unsubstituted heteroarylene group having 2 to 20 carbonatoms, a1 and a2 are the same as and different from each other and areeach independently an integer of 1 to 10, or 1 to 5, and b1 and b2 arethe same as or different from each other and are each independently aninteger of 1 to 5, or 1 to 3.

In Chemical Formula 4, the crystalline polymer block (derived fromterephthaloyl chloride or terephthalic acid) having the number ofrepeating units of a1 or a2 may form individual crystals whose averageparticle size measured by the small-angle X-ray scattering apparatus is8.0 nm or less. In addition, in Chemical Formula 4, the amorphouspolymer block (derived from isophthaloyl chloride, isophthalic acid orphthaloyl chloride, phthalic acid) having the number of repeating unitsof b1 or b2 may form an amorphous polymer chain existing betweenindividual crystals whose average particle size measured by asmall-angle X-ray scattering apparatus is 8.0 nm or less.

That is, the polyamide resin may include a first polyamide segmentincluding a repeating unit represented by Chemical Formula 1 or a blockcomposed thereof; and a second polyamide segment including a repeatingunit represented by Chemical Formula 2, or a block composed thereof,wherein the first polyamide segment and the second polyamide segment mayform a main chain including an alternating repeating unit represented byChemical Formula 3.

The present inventors have found through experiments that as the averageparticle size of the individual crystals is reduced to 8.0 nm or less asin the polyamide resin of one embodiment, it is possible to minimize thegrowth of the length of the polymer block (hereinafter, referred to asthe first polyamide segment) consisting of repeating units derived fromterephthaloyl chloride or terephthalic acid in the polyamide resin andlower the crystallinity of the polyamide resin, thus implementing atransparent polyamide resin. The present invention has been completed onthe basis of such finding.

Specifically, in the main chain of the polyamide resin, crystallinepolymer blocks derived from terephthaloyl chloride or terephthalic acid(hereinafter, referred to as first polyamide segment) and amorphouspolymer blocks derived from isophthaloyl chloride, isophthalic acid orphthaloyl chloride, phthalic acid (hereinafter, referred to as secondpolyamide segment) may alternately form a polymer chain. That is, thesecond polyamide segment is positioned between the first polyamidesegments, and may serve to suppress the growth of the length of thefirst polyamide segment.

In this case, the first polyamide segment is included in the individualcrystals of the polyamide resin to express crystal properties, and thesecond polyamide segment is included in an amorphous polymer chainbetween the individual crystals to express amorphous properties.

Therefore, when the length growth of the first polyamide segment issuppressed, the average particle size of the individual crystalsmeasured by a small-angle X-ray scattering apparatus is measured to berelatively small. Since the polyamide resin can remarkably reduce thehaze value while reducing the crystal characteristics of the firstpolyamide segment, it is possible to achieve excellent transparency.

On the contrary, when the length growth suppression effect of the firstpolyamide segment by the second polyamide segment is reduced, and thelength growth of the first polyamide segment proceeds excessively, theaverage particle size of the individual crystals measured by thesmall-angle X-ray scattering apparatus is measured to be relativelylarge, the polyamide resin may have poor transparency while increasingthe crystal characteristics of the first polyamide segment and rapidlyincreasing the haze value.

And yet, the polyamide resin can have a sufficient level of weightaverage molecular weight, whereby a sufficient level of mechanicalproperties can also be achieved.

Meanwhile, the polyamide resin may have a degree of crystallinity of 20%or less, or 1% to 20%, as measured by a small-angle X-ray scatteringapparatus. The degree of crystallinity of the polyamide resin can bemeasured through an analytical instrument by fitting a scatteringpattern obtained by irradiating X-rays with energies of 10 KeV to 20KeV, or 10 KeV to 14 KeV, or 16 KeV to 20 KeV in a small-angle X-rayscattering apparatus to a solid sphere model. The small-angle X-rayscattering apparatus and the analysis contents thereof include thecontents described above in the average particle size of the individualcrystals.

The weight average molecular weight of the polyamide resin may be 330000g/mol or more, 420000 g/mol or more, or 500000 g/mol or more, or 330000g/mol to 1000000 g/mol, or 420000 g/mol to 1000000 g/mol, or 500000g/mol to 1000000 g/mol, or 420000 g/mol to 800000 g/mol, or 420000 g/molto 600000 g/mol, or 450000 g/mol to 550000 g/mol.

The reason why the weight average molecular weight of the polyamideresin is measured to be high is considered to be due to the formation ofa melt-kneaded complex in the preparation method of the polyamide resinof another embodiment of the present invention described hereinafter.When the weight average molecular weight is reduced to less than 330,000g/mol, the polyamide resin has a problem that mechanical properties suchas flexibility and pencil hardness are lowered.

The polydispersity index of the polyamide resin may be 3.0 or less, or2.9 or less, or 2.8 or less, or 1.5 to 3.0, or 1.5 to 2.9, or 1.6 to2.8, or 1.8 to 2.8. Through such narrow range of polydispersity index,the polyamide resin can improve mechanical properties such as bendingproperties or hardness properties. When the polydispersity index of thepolyamide resin becomes too wide by more than 3.0, there is a limit thatit is difficult to improve the above-described mechanical properties toa sufficient level.

The haze of the polyamide resin measured according to ASTM D1003 may be3.0% or less, or 1.5% or less, 1.00% or less, or 0.85% or less, or 0.10%to 3.0%, or 0.10% to 1.5%, or 0.10% to 1.00%, or 0.50% to 1.00%, or0.80% to 1.00%, or 0.81% to 0.97%. When the haze of the polyamide resinmeasured according to ASTM D1003 is increased by more than 3.0%, theopacity is increased and thus it is difficult to secure a sufficientlevel of transparency. The polyamide resin may have a haze valuemeasured for a specimen having a thickness of 45 μm or more and 55 μm orless according to ASTM D1003 of 3.0% or less.

Preferably, the polyamide resin satisfies the weight average molecularweight of 330000 g/mol or more, 420000 g/mol or more, or 500000 g/mol ormore, or 330000 g/mol to 1000000 g/mol, or 420000 g/mol to 1000000g/mol, or 500000 g/mol to 1000000 g/mol, or 420000 g/mol to 800000g/mol, or 420000 g/mol to 600000 g/mol, or 450000 g/mol to 550000 g/mol,and simultaneously it may have the haze measured according to ASTM D1003of 3.0% or less, or 1.5% or less, 1.00% or less, or 0.85% or less, or0.10% to 3.0%, or 0.10% to 1.5%, or 0.10% to 1.00%, or 0.50% to 1.00%,or 0.80% to 1.00%, or 0.81% to 0.97%.

The relative viscosity of the polyamide resin (measured according toASTM D 2196) may be 45000 cps or more, or 60000 cps or more, or 45000cps to 500000 cps, or 60000 cps to 500000 cps, or 70000 cps to 400000cps, or 80000 cps to 300000 cps, or 100000 cps to 200000 cps, or 110000cps to 174000 cps. When the relative viscosity of the polyamide resin(measured according to ASTM D 2196) is reduced to less than 45000 cps,there is a limit that in the film molding process using the polyamideresin, the molding processability is lowered and the efficiency of themolding process is lowered.

As an example of a method for preparing the polyamide resin of oneembodiment, a method for preparing a polyamide resin including a step ofmelt-kneading a compound represented by the following Chemical Formula 7and a compound represented by the following Chemical Formula 8, andsolidifying the melt-kneaded product to form a complex; and a step ofreacting the complex with an aromatic diamine monomer can be used.

in Chemical Formulas 7 to 8, X is a halogen or a hydroxyl group.

The present inventors have found through experiments that when thecompound represented by Chemical Formula 7 and the compound representedby Chemical Formula 8 are mixed at a temperature equal to or higher thanthe melting point as in the method for preparing the polyamide resin, itis possible to prepare a complex of monomers mixed uniformly through themelting of the compound represented by Chemical Formula 7 and thecompound represented by Chemical Formula 8, and that as this complex isreacted with an aromatic diamine monomer, an amide repeating unitderived from the compound represented by Chemical Formula 7, or a blockcomposed thereof, and an amide repeat uniting derived from the compoundrepresented by Chemical Formula 8, or a block composed thereof can bealternatively polymerized, thereby completing the present invention.

That is, the polyamide resin of one embodiment can be obtained by thepreparation method of the polyamide resin.

Specifically, each of the compound represented by Chemical Formula 7 andthe compound represented by Chemical Formula 8 exhibits differentaspects in solubility and reactivity due to chemical structuraldifferences. Therefore, even when they are added simultaneously, thereis a limit in that the amide repeating unit derived from the compoundrepresented by Chemical Formula 7 is predominantly formed and longblocks are formed, thereby increasing the crystallinity of the polyamideresin and making it difficult to secure transparency.

Thus, in the preparation method of the polyamide resin, the compoundrepresented by Chemical Formula 7 and the compound represented byChemical Formula 8 are not simply physically mixed, but through theformation of a complex by melt-kneading at a temperature higher thaneach melting point, each monomer was induced to react relatively evenlywith the aromatic diamine monomer.

Meanwhile, when synthesizing existing polyamide resin, as the compoundrepresented by Chemical Formula 7 and the compound represented byChemical Formula 8 are dissolved in a solvent and then reacted with anaromatic diamine monomer in a solution state, there was a limit in thatdue to the deterioration by moisture or mixing in solvents, themolecular weight of the finally synthesized polyamide resin decreases.Further, due to the difference in the solubility of the compoundrepresented by Chemical Formula 7 and the compound represented byChemical Formula 8, the amide repeating unit derived from the compoundrepresented by Chemical Formula 7 is predominantly formed and longblocks are formed, thereby increasing the crystallinity of the polyamideresin and making it difficult to secure transparency.

Thus, in the preparation method of the polyamide resin, as a complexobtained by melt-kneading the compound represented by Chemical Formula 7and the compound represented by Chemical Formula 8 are reacted with thearomatic diamine monomer dissolved in the organic solvent in the form ofa solid powder through cooling at a temperature lower than each meltingpoint (minus 10° C. to plus 30° C., or 0° C. to plus 30° C., or plus 10°C. to plus 30° C.), the molecular weight of the finally synthesizedpolyamide resin was confirmed to be improved, and it was confirmedthrough experiments that excellent mechanical properties are secured.

Specifically, the method for preparing the polyamide resin may includemelt-kneading the compound represented by Chemical Formula 7 and thecompound represented by Chemical Formula 8, and solidifying themelt-kneaded product to form a complex.

In the compound represented by Chemical Formula 7, X is a halogen or ahydroxyl group. Preferably, in Chemical Formula 7, X is chlorine.Specific examples of the compound represented by Chemical Formula 7include terephthaloyl chloride or terephthalic acid.

The compound represented by Chemical Formula 7 may form a repeating unitrepresented by Chemical Formula 1 by an amidation reaction of anaromatic diamine monomer. Due to the linear molecular structure, thechain packing and alignment can be kept constant in the polymer, and thesurface hardness and mechanical properties of the polyamide film can beimproved.

In the compound represented by Chemical Formula 8, X is a halogen or ahydroxyl group. Preferably, in Chemical Formula 8, X is chlorine.Specific examples of the compound represented by Chemical Formula 8include phthaloyl chloride, phthalic acid, isophthaloyl chloride, orisophthalic acid.

The compound represented by Chemical Formula 8 may form a repeating unitrepresented by Chemical Formula 2 by an amidation reaction of anaromatic diamine monomer. Due to the curved molecular structure, it hasthe property of interfering with chain packing and alignment within thepolymer, and it is possible to increase the amorphous region in thepolyamide resin and thus improve the optical properties and the foldingendurance of the polyamide film. In addition, as this is included in thepolyamide resin together with the repeating unit represented by ChemicalFormula 1, it is possible to increase the molecular weight of thepolyamide resin.

Meanwhile, in the step of melt-kneading a compound represented byChemical Formula 7 and a compound represented by Chemical Formula 8, andsolidifying the melt-kneaded product to form a complex, themelt-kneading means mixing the compound represented by Chemical Formula7 and the compound represented by Chemical Formula 8 at a temperatureequal to or higher than the melting point.

In this manner, the compound represented by Chemical Formula 7 and thecompound represented by Chemical Formula 8 are not simply physicallymixed, but through the formation of a complex by melt-kneading at atemperature higher than each melting point, each monomer was induced toreact relatively evenly with the aromatic diamine monomer.

Due to the difference in the solubility of the compound represented byChemical Formula 7 and the compound represented by Chemical Formula 8,the amide repeating unit derived from the compound represented byChemical Formula 7 is predominantly formed and long blocks are formed,thereby increasing the crystallinity of the polyamide resin and makingit difficult to secure transparency. Therefore, in order to solve theselimitations, the first polyamide segment and the second polyamidesegment can alternately form a main chain includingalternating-repeating units represented by Chemical Formula 3 as in oneembodiment.

At this time, with respect to 100 parts by weight of the compoundrepresented by Chemical Formula 7, the compound represented by ChemicalFormula 8 may be mixed at 5 parts by weight to 60 parts by weight, or 5parts by weight to 50 parts by weight, or 5 parts by weight to 25 partsby weight, or 10 parts by weight to 30 parts by weight, or 15 parts byweight to 25 parts by weight. Thereby, the technical effect ofincreasing transmittance and clarity can be realized. When the compoundrepresented by Chemical Formula 8 is mixed in an excessively smallamount of less than 5 parts by weight with respect to 100 parts byweight of the compound represented by Chemical Formula 7, the technicalproblems such as becoming opaque and the increase of haze may occur.When the compound represented by Chemical Formula 8 is mixed in anexcessively high amount of more than 60 parts by weight with respect to100 parts by weight of the compound represented by Chemical Formula 7,the technical problems such as the reduction of physical properties(hardness, tensile strength, etc.) may occur.

In addition, in forming the complex by solidifying the molt-kneadedproduct, the solidifying means a physical change in which themolt-kneaded product in the molten state is cooled to a temperatureequal to or less than the melting point and solidified. Thereby, theformed complex may be in a solid state. More preferably, the complex maybe a solid powder obtained through an additional grinding process or thelike.

Meanwhile, the step of melt-kneading a compound represented by ChemicalFormula 7 and a compound represented by Chemical Formula 8, andsolidifying the melt-kneaded product to form a complex may include astep of mixing the compound represented by Chemical Formula 7 and thecompound represented by Chemical Formula 8 at a temperature of 50° C. orhigher; and a step of cooling the result of the mixing step.

The terephthaloyl chloride has a melting point of 81.3° C. to 83° C.,the isophthaloyl chloride has a melting point of 43° C. to 44° C., andthe phthaloyl chloride may have a melting point of 6° C. to 12° C.Thereby, when these are mixed at a temperature of 50° C. or higher, or90° C. or higher, or 50° C. to 120° C., or 90° C. to 120° C., or 95° C.to 110° C., or 100° C. to 110° C., melt-kneading may be performed underthe condition of temperature higher than the melting point of both thecompound represented by Chemical Formula 7 and the compound representedby Chemical Formula 8.

In the step of cooling the result of the mixing step, the result of themelt-kneading step is left at plus 5° C. or below, or minus 10° C. toplus 5° C., or minus 5° C. to plus 5° C., which is a temperaturecondition lower than the melting point of both the compound representedby Chemical Formula 7 and the compound represented by Chemical Formula8, so that a more uniform solid powder can be obtained through cooling.

Meanwhile, after the step of cooling the result of the mixing step, themethod may further include a step of grinding the result of the coolingstep. Through the grinding step, a solid complex can be prepared inpowder form, and the powder obtained after the grinding step may have anaverage particle size of 1 mm to 10 mm.

Grinders used for grinding with such particle sizes specifically includea pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, a jogmill or sieve, a jaw crusher, and the like, but are not limited to theexamples described above.

In this manner, as the melt mixture of the compound represented byChemical Formula 7 and the compound represented by Chemical Formula 8 isreacted with the aromatic diamine monomer in the form of solids,specifically solid powders, through the cooling at a temperature lowerthan the melting point, the deterioration the compound represented byChemical Formula 7 and the compound represented by Chemical Formula 8due to moisture or their mixing in solvents is minimized, the molecularweight of the finally synthesized polyamide resin is increased, andthereby excellent mechanical properties of the polyamide resin can beensured.

In addition, after the step of melt-kneading a compound represented bythe following Chemical Formula 7 and a compound represented by thefollowing Chemical Formula 8, and solidifying the melt-kneaded productto form a complex, the method for preparing the polyamide resin mayinclude a step of reacting the complex with an aromatic diamine monomer.

The reaction in the step of reacting the complex with an aromaticdiamine monomer may be performed under an inert gas atmosphere at atemperature condition of minus 25° C. to 25° C. or a temperaturecondition of minus 25° C. to 0° C.

Specific examples of the aromatic diamine monomer include at least oneselected from the group consisting of2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine,2,2′-dimethyl-4,4′-diaminobenzidine, 4,4′-diaminodiphenyl sulfone,4,4′-(9-fluorenylidene)dianiline, bis(4-(4-aminophenoxy)phenyl)sulfone,2,2′,5,5′-tetrachlorobenzidine, 2,7-diaminofluorene,4,4-diaminooctafluorobiphenyl, m-phenylenediamine, p-phenylenediamine,4,4′-oxydianiline, 2,2′-dimethyl-4,4′-diaminobiphenyl,2,2-bis[4-(4-aminophenoxy)phenyl]propane,1,3-bis(4-aminophenoxy)benzene, m-xylylenediamine, p-xylylenediamine and4,4′-diaminobenzanilide.

More preferably, as the aromatic diamine monomer,2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB),2,2′-dimethyl-4,4′-diaminobenzidine, m-xylylenediamine, orp-xylylenediamine can be used.

More specifically, the step of reacting the complex with an aromaticdiamine monomer may include a step of dissolving the aromatic diaminemonomer in an organic solvent to prepare a diamine solution; and a stepof adding a complex powder to the diamine 10 solution.

In the step of dissolving the aromatic diamine monomer in an organicsolvent to prepare a diamine solution, the aromatic diamine monomerincluded in the diamine solution may be present in a state dissolved inan organic solvent. Examples of the solvent are not particularlylimited, but for example, common general-purpose organic solvents suchas N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide,N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylpropionamide,3-methoxy-N,N-dimethylpropionamide, dimethyl sulfoxide, acetone,N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, tetrahydrofuran,chloroform, gamma-butyrolactone, ethyl lactate, methyl3-methoxypropionate, methyl isobutyl ketone, toluene, xylene, methanol,ethanol, or the like can be used without limitation.

In the step of adding a complex powder to the diamine solution, thecomplex powder will react with the aromatic diamine monomer dissolved inthe diamine solution. As a result, the deterioration the compoundrepresented by Chemical Formula 7 and the compound represented byChemical Formula 8 due to moisture, or their mixing in solvents isminimized, the molecular weight of the finally synthesized polyamideresin is increased, and thereby excellent mechanical properties of thepolyamide resin can be ensured.

After the step of cooling the result of the mixing step, the complexpowder can prepare a complex of solids in the form of powder through thestep of grinding the result of the cooling step. The powder obtainedafter the grinding step may have an average particle size of 1 mm to 10mm.

II. Polymer Film

According to the other embodiment of the invention, there may beprovided a polymer film comprising the polyamide resin of oneembodiment.

The details concerning the polyamide resin can include all of thosedescribed in the one embodiment.

More specifically, the polymer film may include a polyamide resin of oneembodiment or a cured product thereof. The cured product means amaterial obtained through a curing process of the polyamide resin of theone embodiment.

When the polymer film is prepared using the polyamide resin of the oneembodiment, excellent optical and mechanical properties can be realized,and simultaneously flexibility can be provided, so that it can be usedas a material for various molded articles. For example, the polymer filmmay be applied to a display substrate, a display protective film, atouch panel, a window cover of a foldable device, and the like.

The thickness of the polymer film is not particularly limited, but forexample, it can be freely adjusted within the range of 0.01 μm to 1000μm. When the thickness of the polymer film increases or decreases by aspecific value, the physical properties measured in the polymer film mayalso change by a certain value.

The polymer film may be prepared by a conventional method such as a drymethod or a wet method using the polyamide resin of the one embodiment.For example, the polymer film may be formed by a method of coating asolution containing the polyamide resin of one embodiment on anarbitrary support to form a film, evaporating the solvent from themembrane and drying it. If necessary, stretching and heat treatment ofthe polymer film may be further performed.

As the polymer film is produced using the polyamide resin of the oneembodiment, it may exhibit excellent mechanical properties while beingcolorless and transparent.

Specifically, the polymer film has a haze value measured for a specimenhaving a thickness of 50±2 μm according to ASTM D1003 of 3.0% or less,or 1.5% or less, 1.00% or less, or 0.85% or less, or 0.10% to 3.0%, or0.10% to 1.5%, or 0.10% to 1.00%, or 0.50% to 1.00%, or 0.80% to 1.00%,or 0.81% to 0.97%. When the haze the polymer film measured according toASTM D1003 is increased by more than 3.0%, the opacity is increased andthus it is difficult to secure a sufficient level of transparency.

The polymer film has a yellowness index (YI) measured for a specimenhaving a thickness of 50±2 μm according to ASTM E313 of 4.0 or less, or3.0 or less, or 0.5 to 4.0, or 0.5 to 3.0. When the yellowness index(YI) of the polymer film measured according to ASTM E313 is increased bymore than 4.0, the opacity is increased and thus it is difficult tosecure a sufficient level of transparency.

Further, the polymer film may have a transmittance (T, @550 nm) forvisible light at wavelength of 550 nm for a specimen having a thicknessof 50±2 μm of 86% or more, or 86% to 90%. The transmittance (T, @388 nm)for UV light at wavelength of 388 nm may be 50.00% or more, or 60.00% ormore.

Further, the polymer film may have a folding endurance measured for aspecimen having a thickness of 50±2 μm (the number of reciprocatingbending cycles at an angle of 135°, a rate of 175 rpm, a radius ofcurvature of 0.8 mm and a load of 250 g) of 4000 cycles or more, or 7000cycles or more, or 9000 cycles or more, or 4000 cycles to 20000 Cycles,or 7000 cycles to 20000 cycles, or 9000 cycles to 20000 cycles.

Further, the polymer film may have a pencil hardness value measured fora specimen having a thickness of 50±2 μm according to ASTM D3363 of 1Hor more, or 3H or more, or 1H to 4H, or 3H to 4H.

III. Resin Laminate

According to another aspect of the present invention, there can beprovided a resin laminate including a substrate including a polyamideresin in which an average particle size of individual crystals measuredby a small-angle X-ray scattering apparatus is 8.0 nm or less; and ahard coating layer formed on at least one side of the substrate.

The substrate may include the polyamide resin of one embodiment, and itmay also include a polymer film of the other embodiment. The detailsconcerning the polyamide resin may include all of those described in theone embodiment, and the details concerning the polymer film may includeall of those described in the other embodiment.

A hard coating layer may be formed on at least one side of thesubstrate. A hard coating layer may be formed on one side or both sidesof the substrate. When the hard coating layer is formed only on one sideof the substrate, a polymer film including one or more polymers selectedfrom the group consisting of polyimide-based, polycarbonate-based,polyester-based, polyalkyl(meth)acrylate-based, polyolefin-based andpolycyclic olefin-based polymers may formed on the opposite side of thesubstrate.

The hard coating layer may have a thickness of 0.1 μm to 100 μm.

The hard coating layer can be used without particular limitation as longas it is a material known in the field of hard coating. For example, thehard coating layer may include a binder resin of photocurable resin; andinorganic particles or organic particles dispersed in the binder resin.

The photocurable resin contained in the hard coating layer is a polymerof a photocurable compound which can cause a polymerization reactionwhen irradiated with light such as ultraviolet rays, and may be oneconventionally used in the art. However, preferably, the photocurablecompound may be a polyfunctional (meth)acrylate monomer or oligomer.

At this time, it is advantageous in terms of ensuring the physicalproperties of the hard coating layer that the number of(meth)acrylate-based functional groups is 2 to 10, 2 to 8, or 2 to 7.Alternatively, the photocurable compound may be at least one selectedfrom the group consisting of pentaerythritol tri(meth)acrylate,pentaerythritol tetra(meth)acrylate, dipentaerythritolpenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate,dipentaerythritol hepta(meth)acrylate, tripentaerythritolhepta(meth)acrylate, trilene diisocyanate, xylene diisocyanate,hexamethylene diisocyanate, trimethylolpropane tri(meth)acrylate, andtrimethylolpropane polyethoxy tri(meth)acrylate.

The inorganic particles may be, for example, silica, metal atoms such assilica, aluminum, titanium, or zinc, or oxides or nitrides thereof.Silica fine particles, aluminum oxide particles, titanium oxideparticles, zinc oxide particles, and the like can be used independentlyof each other.

The inorganic particles may have an average radius of 100 nm or less, or5 to 100 nm. The type of the organic particles is not limited, and forexample, polymer particles having an average particle size of 10 nm to100 μm may be used.

The resin laminate can be used as a substrate or a cover window of adisplay device, or the like. It has high flexibility and bendingdurability together with high transmittance and low haze properties, sothat it can be used as a substrate or cover window of a flexible displaydevice. That is, the display device including the resin laminate, or theflexible display device including the resin laminate may be implemented.

Advantageous Effects

According to the present invention, there can be provided a polyamideresin that can secure at least an adequate level of mechanicalproperties while improving transparency by suppressing excessive growthof the length of crystalline polymer chains, and a polymer film andresin laminate using the same.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic diagram of the crystal structure of thepolyamide resin obtained in (1) of Example 1.

FIG. 2 shows a ¹³C-NMR spectrum of the polyamide resin obtained in (1)of Example 1.

FIG. 3 shows a ¹³C-NMR spectrum of the polyamide resin obtained in (1)of Example 2.

FIG. 4 schematically shows formation of individual crystals by gatheringpolyamide resin chains in a bundle.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described inmore detail by way of examples. However, these examples are presentedfor illustrative purposes only, and are not intended to limit the scopeof the present invention.

PREPARATION EXAMPLE: PREPARATION OF ACYL CHLORIDE COMPLEX PreparationExample 1

549.4 g (2.704 mol) of terephthaloyl chloride (TPC: melting point: 83°C.) and 120.6 g (0.594 mol) of isophthaloyl chloride (IPC; meltingpoint: 44° C.) were added to a 1000 mL 4-neck round flask (reactor)equipped with a stirrer, a nitrogen injection device, a dropping funneland a temperature controller, and the mixture was melt-kneaded at 100°C. for 3 hours and then cooled at 0° C. for 12 hours to prepare acomplex of acylchloride (specifically, terephthaloyl chloride andisophthaloyl chloride).

Subsequently, the acyl chloride complex was grinded with a jaw crusherto prepare a powder having an average particle size of 5 mm.

Preparation Example 2

An acylchloride complex was prepared in the same manner as inPreparation Example 1, except that 569.5 g (2.803 mol) of terephthaloylchloride (TPC: melting point: 83° C.) and 100.5 g (0.495 mol) ofisophthaloyl chloride (IPC: melting point: 44° C.) were added.

EXAMPLE: PREPARATION OF POLYAMIDE RESIN AND POLYMER FILM Example 1

(1) Polyamide Resin

262 g of N,N-dimethylacetamide (DMAc) was filled into a 500 mL 4-neckround flask (reactor) equipped with a stirrer, a nitrogen injectiondevice, a dropping funnel and a temperature controller while slowlyblowing nitrogen into the reactor. Then, the temperature of the reactorwas adjusted to 0° C., and 14.153 g (0.0442 mol) of2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB) was added anddissolved.

The mixture was stirred while adding 8.972 g (0.0442 mol) of the acylchloride complex powder obtained in Preparation Example 1, and subjectedto amide formation reaction at 0° C. for 12 hours.

After completion of the reaction, N,N-dimethylacetamide (DMAc) was addedto dilute the solution to a solid content of 5% or less, and theresultant was precipitated with 1 L of methanol. The precipitated solidswere filtered and then dried at 100° C. under vacuum for 6 hours or moreto prepare a solid-state polyamide resin.

It was confirmed through ¹³C-NMR shown in FIG. 2 that the polyamideresin obtained in (1) of Example 1, contained 82 mol % of the firstrepeating unit obtained by an amide reaction of terephthaloyl chloride(TPC) and 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB) and 18mol % of the second repeating unit obtained by an amide reaction ofisophthaloyl chloride (IPC) and2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB).

(2) Polymer Film

The polyamide resin obtained in (1) of Example 1 was dissolved inN,N-dimethylacetamide to prepare about 10% (w/v) polymer solution.

The polymer solution was applied onto a polyimide base film (UPILEX-75s,UBE), and the thickness of the polymer solution was uniformly adjustedusing a film applicator.

Then, after drying for 15 minutes at 80° C. Mathis oven, it was curedfor 30 minutes at 250° C. while flowing nitrogen, and peeled from thesubstrate film to obtain a polymer film.

Example 2

(1) Polyamide Resin

A polyamide resin was prepared in the same manner as in (1) of Example1, except that the acyl chloride complex powder obtained in PreparationExample 2 was used instead of the acyl chloride complex powder obtainedin Preparation Example 1.

It was confirmed through ¹³C-NMR shown in FIG. 3 that the polyamideresin obtained in (1) of Example 2, contained 85 mol % of the firstrepeating unit obtained by an amide reaction of terephthaloyl chloride(TPC) and 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB), and 15mol % of the second repeating unit obtained by an amide reaction ofisophthaloyl chloride (IPC) and2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB).

(2) Polymer Film

A polymer film was prepared in the same manner as in (2) of Example 1,except that the polyamide resin obtained in (1) of Example 2 was usedinstead of the polyamide resin obtained in (1) of Example 1.

COMPARATIVE EXAMPLE: PREPARATION OF POLYAMIDE RESIN AND POLYMER FILMComparative Example 1

(1) Polyamide Resin

A polyamide resin was prepared in the same manner as in (1) of Example1, except that instead of the acyl chloride complex powder obtained inPreparation Example 1, 7.358 g (0.0362 mol) of terephthaloyl chloride(TPC) and 1.615 g (0.0080 mol) of isophthaloyl chloride (IPC) were addedsimultaneously to perform an amide formation reaction.

(2) Polymer Film

A polymer film was prepared in the same manner as in (2) of Example 1,except that the polyamide resin obtained in (1) of Comparative Example 1was used instead of the polyamide resin obtained in (1) of Example 1.

Comparative Example 2

(1) Polyamide Resin

A polyamide resin was prepared in the same manner as in (1) of Example1, except that instead of the acyl chloride complex powder obtained inPreparation Example 1, 7.358 g (0.0362 mol) of terephthaloyl chloride(TPC) was first added, and then 1.615 g (0.0080 mol) of isophthaloylchloride (IPC) was added sequentially at about 5 minute intervals toperform an amide formation reaction.

(2) Polymer Film

A polymer film was prepared in the same manner as in (2) of Example 1,except that the polyamide resin obtained in (1) of Comparative Example 2was used instead of the polyamide resin obtained in (1) of Example 1.

Comparative Example 3

(1) Polyamide Resin

A polyamide resin was prepared in the same manner as in (1) of Example1, except that instead of the acyl chloride complex powder obtained inPreparation Example 1, 1.615 g (0.0080 mol) of isophthaloyl chloride(IPC) was first added, and then 7.358 g (0.0362 mole) of terephthaloylchloride (TPC) was added sequentially at about 5 minute intervals toperform an amide formation reaction.

(2) Polymer Film

A polymer film was prepared in the same manner as in (2) of Example 1,except that the polyamide resin obtained in (1) of Comparative Example 3was used instead of the polyamide resin obtained in (1) of Example 1.

Experimental Example 1

The properties of the individual crystals contained in the polyamideresins obtained in Examples and Comparative Examples were measured bythe following method using a small-angle X-ray scattering method (SAXS),and the results are shown in Table 1 below.

The polymer films obtained in Examples and Comparative Examples wereused to prepare a sample with a size of 1 cm in width*1 cm in length.The sample was set on a small angle X-ray scattering apparatus (PLS-9AUSAXS beam line) having a camera length of 2.5 m, 6.5 m at roomtemperature (23° C.), and irradiated with X-rays having an energy of11.1 KeV, 19.9 KeV to obtain a scattering pattern. The scatteringpattern was analyzed through the analysis equipment (NIST SANS package)mounted on the small angle X-ray scattering apparatus to determine theaverage particle size (2Rc), dimensionality, and crystallinity of theindividual crystals.

Specifically, the analysis of the average particle size (2Rc),dimensionality, and crystallinity of the individual crystals wasperformed through a computer program (NIST SANS package) using the dataobtained from a small angle X-ray scattering apparatus (PLS 9Abeamline). More specifically, the average particle size of theindividual crystals can be obtained through the calculation of computerprogram (NIST SANS package) for the diameter distribution curve ofcrystals which is obtained by fitting the shape of individual crystalscontained in the sample to a solid sphere model, plotting the obtainedwavenumber q (unit: Å⁻¹) and scattering intensity I (unit: a.u.), andconvoluting the plot with a Schulz-Zimm distribution.

TABLE 1 Average particle size Dimen- Degree of of crystals (nm)sionality crystallinity (%) Example 1 5.0 3.7 Difficult to measure atless than 20% Example 2 6.8 — Difficult to measure at less than 20%Comparative 8.4 4.0 Difficult to measure Example 1 at less than 20%Comparative 13.4 3.2 24 Example 2 Comparative 8.1 — Difficult to measureExample 3 at less than 20%

As shown in Table 1, it could be confirmed that the average particlesize of the individual crystals contained in the polyamide resinobtained in Examples was measured to be as small as 5 nm to 6.8 nm,whereas the average particle size of the individual crystals containedin the polyamide resin obtained in Comparative Example 1 was 8.4 nm, theaverage particle size of the individual crystals contained in thepolyamide resin obtained in Comparative Example 2 was 13.4 nm, and theaverage particle size of the individual crystals contained in thepolyamide resin obtained in Comparative Example 3 was 8.1 nm, whichincreased as compared to Examples. In addition, it was confirmed thatthe crystallinity of the polyamide resin obtained in Examples showed alow degree of crystallinity of less than 20%, while the degree ofcrystallinity of the polyamide resin obtained in Comparative Example 2was 24%, which increased compared to Examples. Thereby, it was confirmedthat in the case of the polyamide resin obtained in Examples, the growthof the length of the crystalline block consisting of a repeating unitobtained by an amide reaction of terephthaloyl chloride (TPC) and2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine (TFDB) was suppressedcompared with Comparative Examples.

Experimental Example 2

The following characteristics were measured or evaluated for thepolyamide resins or the polymer films obtained in the above examples andcomparative examples, and the results are shown in Table 2 below.

(1) Thickness: The thickness of the polymer film was measured using athickness measuring device.

(2) Yellowness index (Y.I.): The yellowness index of the polymer filmwas measured according to the measurement method of ASTM E313 using aCOH-400 Spectrophotometer (NIPPON DENSHOKU INDUSTRIES).

(3) Transmittance: The total light transmittance of the polymer film wasmeasured using a Shimadzu UV-2600 UV-vis spectrometer. In themeasurement results, the transmittance (T, @388 nm) for ultravioletlight at a wavelength of 388 nm and the transmittance (T, @550 nm) forvisible light at wavelength of 550 nm were shown.

(4) Haze: The haze value of the polymer film was measured according tothe ASTM D1003 test method using a COH-400 Spectrophotometer (NIPPONDENSHOKU INDUSTRIES).

(5) Molecular weight and polydispersity index (PDI): The weight averagemolecular weight (Mw) and the number average molecular weight (Mn) ofthe polyamide resin were measured by gel permeation chromatography (GPC,manufactured by Waters), and the polydispersity index (PDI) wascalculated by dividing the weight average molecular weight by the numberaverage molecular weight. Specifically, the measurement was performedusing a 600 mm long column connecting two Polymer Laboratories PLgelMIX-B Columns (300 mm in length), through Waters 2605 Refractive Index(RI) Detector, wherein the evaluation temperature was 50 to 75° C.(about 65° C.), DMF 100 wt % solvent was used, the flow rate was 1mL/min, and the sample was prepared at a concentration of 1 mg/mL andsupplied in an amount of 100 μL for 25 minutes. The molecular weightscould be determined using calibration curves formed using polystyrenestandards. As the molecular weight of polystyrene standard products, 7types of 3940/9600/31420/113300/327300/1270000/4230000 were used.

(6) Bending Property: The folding endurance of the polymer films wasevaluated using an MIT type folding endurance tester. Specifically, aspecimen (1 cm*7 cm) of the polymer film was loaded into the foldingendurance tester, and folded to an angle of 135° at a rate of 175 rpm onthe left and right sides of the specimen, with a radius of curvature of0.8 mm and a load of 250 g, until the specimen was bended and fractured.The number of reciprocating bending cycles was measured as the foldingendurance.

(7) Viscosity: Under a constant reflux system at 25*0.2° C., theviscosity of the solution containing polyamide resin (solvent:dimethylacetamide (DMAc), solid content: 10 wt %) was measured accordingto ASTM D 2196: test method of non-Newtonian materials by BrookfieldDV-2T Rotational Viscometer. As Brookfield silicone standard oil, anumber of standard solutions having a viscosity range of 5000 cps to200000 cps was used. The measurement was performed with a spindle LV-4(64), 0.3-100 RPM, and the unit was cps (mPa·s).

(8) Pencil Hardness: The pencil hardness of the polymer films wasmeasured according to the ASTM D3363 test method using a Pencil HardnessTester. Specifically, varying hardness values of pencils were fixed tothe tester and scratched on the polymer film, and the degree ofoccurrence of a scratch on the polymer film was observed with the nakedeye or with a microscope. When more than 70% of the total number ofscratches were not observed, a value corresponding to the hardness ofthe pencil was evaluated as the pencil hardness of the polymer film.

The pencil hardness is increased in the order of B grade, F grade and Hgrade. Within the same grade, the higher the number, the higher thehardness. Within the grade, the higher the number, the higher thehardness.

TABLE 2 Comparative Comparative Comparative Category Example 1 Example 2Example 1 Example 2 Example 3 Thickness (μm) 50 49 51 51 50 Y.I. 2.682.89 8.55 25.10 4.59 T (%)@550 nm 88.75 88.50 85.63 75.94 87.57 T(%)@388 nm 75.3 71.0 51.01 31.62 65.04 Haze(%) 0.81 0.97 3.43 24.21 1.61Mw(g/mol) 512000 463000 412000 350000 382000 Bending property 12022 97855210 785 4513 (Cycle) PDI 1.84 2.71 2.05 2.02 1.98 Viscosity (cps)110000 174000 54000 24000 28000 Pencil hardness 3H 4H 1H F 1H

Looking at Table 2 above, the polyamide resin of Examples prepared usingthe acyl chloride complex powder according to Preparation Examples 1 to2 had a high weight average molecular weight of 463000 g/mol to 512000g/mol, and the relative viscosity was measured to be as high as 110000cps to 174000 cps. Moreover, it was confirmed that the polymer filmobtained from the polyamide resin of Examples had a low yellowness indexof 2.68 to 2.89 and a low haze value of 0.81% to 0.97% at a thickness ofabout 50 μm, thereby exhibiting excellent transparency. It was alsoconfirmed that it had a high pencil hardness of 3H to 4H grade and afolding endurance that was broken at the number of reciprocating bendingcycles from 9785 to 12022, thereby securing excellent mechanicalproperties (scratch resistance and folding endurance).

On the other hand, in the case of the polyamide resins of ComparativeExamples in which the acyl chloride complex powder according toPreparation Examples 1 to 2 was not used in the synthesis process of thepolyamide resin, the molecular weight was reduced from 350,000 g/mol to412,000 g/mol compared to Examples. The viscosity was reduced from24,000 cps to 54,000 cps compared to Examples.

In addition, in the case of the polymer films obtained from thepolyamide resins of Comparative Examples 1, 2, and 3 in which TPC powderand IPC powder were simultaneously or sequentially added, it wasconfirmed that the films had a yellowness index of 4.59 to 25.10 and ahaze value of 1.61% to 24.21% at a thickness of about 50 μm, whichincreased compared to Examples, resulting in poor transparency. This isconsidered to be because, in Comparative Examples 1, 2, and 3, due tothe difference in solubility and reactivity between the TPC powder andthe IPC powder, the block due to TPC is excessively formed, therebyincreasing the crystallinity of the polyamide resin.

EXPLANATION OF SYMBOLS

-   -   1: individual crystals    -   2: average particle size of individual crystals    -   3: amorphous polymer chain

1. A polyamide resin having an average particle size of individualcrystals measured by a small-angle X-ray scattering apparatus is 8.0 nmor less.
 2. The polyamide resin according to claim 1, wherein theaverage particle size of the individual crystals is measured through ananalytical equipment by fitting a scattering pattern obtained byirradiating X-rays with energies of 10 KeV to 20 KeV in the small-angleX-ray scattering apparatus to a solid sphere model.
 3. The polyamideresin according to claim 1, wherein amorphous polymer chains are presentbetween the individual crystals having the average particle size of 8.0nm or less.
 4. The polyamide resin according to claim 3, wherein adistance between the individual crystals having the average particlesize of 8.0 nm or less is 0.1 nm to 100 nm.
 5. The polyamide resinaccording to claim 1, wherein the individual crystals having the averageparticle size of 8.0 nm or less comprises a first aromatic polyamiderepeating unit derived from a combination of a 1,4-aromatic diacylcompound and an aromatic diamine compound.
 6. (canceled)
 7. Thepolyamide resin according to claim 3, wherein the amorphous polymerchain comprises a second aromatic amide repeating unit derived from acombination of a 1,2-aromatic diacyl compound and an aromatic diaminecompound, or a third aromatic amide repeating unit derived from acombination of a 1,3-aromatic diacyl compound and an aromatic diaminecompound.
 8. (canceled)
 9. The polyamide resin according to claim 1,wherein the individual crystals having the average particle size of 8.0nm or less comprises a first polyamide segment including a repeatingunit represented by the following Chemical Formula 1, or a blockcomprised thereof:

in the Chemical Formula 1, Ar₁ is a substituted or unsubstituted arylenegroup having 6 to 20 carbon atoms, or a substituted or unsubstitutedheteroarylene group having 2 to 20 carbon atoms.
 10. The polyamide resinaccording to claim 9, wherein the first polyamide segment has a numberaverage molecular weight of 100 g/mol to 5000 g/mol.
 11. The polyamideresin according to claim 7, wherein the polyamide resin includes 40 mol% to 95 mol % of the first polyamide segment based on the totalrepeating units contained in the polyamide resin.
 12. The polyamideresin according to claim 1, wherein a degree of crystallinity measuredby the small-angle X-ray scattering apparatus is 20% or less.
 13. Thepolyamide resin according to claim 9, wherein amorphous polymer chainspresent between the individual crystals having the average particle sizeof 8.0 nm or less including the first polyamide segment including therepeating unit represented by Chemical Formula 1 or the block composedthereof comprise a second polyamide segment including a repeating unitrepresented by the following Chemical formula 2, or a block composedthereof:

in the Chemical Formula 2, Ar₂ is a substituted or unsubstituted arylenegroup having 6 to 20 carbon atoms, or a substituted or unsubstitutedheteroarylene group having 2 to 20 carbon atoms.
 14. The polyamide resinaccording to claim 13, wherein the first polyamide segment and thesecond polyamide segment form a main chain including analternating-repeating unit represented by the following Chemical Formula3:

in the Chemical Formula 3, A is the first polyamide segment, and B isthe second polyamide segment.
 15. The polyamide resin according to claim1, wherein the polyamide resin has a haze value measured for a specimenhaving a thickness of 45 μm or more and 55 μm or less according to ASTMD1003 of 3.0% or less.
 16. The polyamide resin according to claim 1,wherein the polyamide resin has a weight average molecular weight of atleast 330000 g/mol.
 17. The polyamide resin according to claim 11,wherein a content of the repeating units represented by Chemical Formula2 is 5 mol % to 60 mol %-based on the total repeating units contained inthe polyamide resin.
 18. The polyamide resin according to claim 13,wherein based on the total repeating units contained in the polyamideresin, a content of the repeating units represented by Chemical Formula1 is 60 mol % to 95 mol %, and the content of the repeating unitsrepresented by Chemical Formula 2 is 5 mol % to 40 mol %.
 19. Thepolyamide resin according to claim 13, wherein the repeating unitrepresented by Chemical Formula 2 comprises a repeating unit representedby the following Chemical Formula 2-1; or a repeating unit representedby Chemical Formula 2-2:

in the Chemical Formulae 2-1 to 2-2, Ar₂ is a substituted orunsubstituted arylene group having 6 to 20 carbon atoms, or asubstituted or unsubstituted heteroarylene group having 2 to 20 carbonatoms.
 20. The polyamide resin according to claim 14, wherein thealternating-repeating unit represented by Chemical Formula 3 is arepeating unit represented by the following Chemical Formula 4:

in the Chemical Formula 4, Ar₁ and Ar₂ are each independently asubstituted or unsubstituted arylene group having 6 to 20 carbon atoms,or a substituted or unsubstituted heteroarylene group having 2 to 20carbon atoms, a1 and a2 are each independently an integer of 1 to 10,and b1 and b2 are each independently an integer of 1 to
 5. 21. A polymerfilm comprising the polyamide resin according to claim
 1. 22. A resinlaminate comprising: a substrate including a polyamide resin having anaverage particle size of individual crystals measured by a small-angleX-ray scattering apparatus is 8.0 nm or less; and a hard coating layerformed on at least one side of the substrate.